Organic oxidizable material containing phenol phosphothionate as an antioxidant



United States Patent 3,451,932 ORGANIC OXIDIZABLE MATERIAL CONTAIN IN GPHENOL PHOSPHOTHIONATE AS AN ANTIOXIDANT Bernard R. Meltsner, Royal Oak,Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation ofVirginia No Drawing. Original application May 20, 1966, Ser. No.551,538. Divided and this application July 23, 1968, Ser. No. 746,759

Int. Cl. Cm 1/48; C08c 11/66; C08f 45/58 US. Cl. 25246.6 15 ClaimsABSTRACT OF THE DISCLOSURE Organic material normally subject tooxidative degradation such as polypropylene is stabilized by theaddition of a tris(3,5-dihydrocarbyl-4-hydroxyphenyl)phosphothionatesuch as tris( 3,5 di tert-butyl-4-hydroxyphenyl) phosphothionate.Effectiveness is synergistically improved by adding dihydrocarbylthiodialkanoates such as dilaurylthiodipropionate.

This application is a division of copending application Ser. No.551,538, filed May 20, 1966.

This invention relates to new 3,5-dihydrocarbyl-4- hydroxyphenylphosphothionates and their use as antioxidants.

Most organic materials undergo degradation in the presence of oxygen.This degradation is accelerated at increased temperatures, Frequently,high temperatures are encountered during the processing of thesematerials in manufacturing operations and thus some form of stabilizeris required for many materials, even during the manufacturing stage.Other materials are not subject to extremes in temperature duringmanufacture, but even these undergo degradation on aging.

An object of this invention is to provide an additive capable ofpreventing degradation of organic materials due to oxygen. A furtherobject of this invention is to provide organic materials that are stableagainst the effects of elevated temperatures during manufacture and alsostable during long periods of aging under use conditions. A particularobject is to provide a polyolefin (e.g., polypropylene) of exceptionalhigh-temperature stability and capable of resisting degradation due tooxygen during long periods of use. Other objects will become apparentfrom the following description of the invention.

The above and other objects are accomplished b providing as a newcomposition of mattertris(3,5-dihydrocarbyl-4-hydroxyphenyl)phosphothionate. These newcompounds have the formula:

wherein R is selected from the group consisting of alphabranched alkylradicals containing from 3 to 18 carbon atoms, alpha-branched aralkylradicals containing from 8 to 18 carbon atoms and cycloalkyl radicalscontaining from 6 to 18 carbon atoms; and R is selected from the groupconsisting of alkyl radicals containing from 1 to 18 carbon atoms,aralkyl radicals containing from 7 to 18 carbon atoms, aryl radicalscontaining from 6 to 18 carbon atoms and cycloalkyl radicals containingfrom 6 to 18 carbon atoms.

The following compounds serve to illustrate these new pliosphothionates.

tris(3methyl-5-tert-butyl-4-hydr0xyphenyl) phosphothionate tris(3-ethyl-5-isopropyl-4-hydroxyphenyl) phosphothionate tris3-methyl-5-cyclohexyl-4-hydroxyphenyl) phosphothionate tris (3-n-propyl-5- a-methylbenzyl -4-hydroxyphenyl) phosphothionate tris(3-methyl-5-( u-methylbenzyl)-4-hydroxyphenyl) phosphothionatetris(3-mcthyl-5-(a,a-dimethylbenzyl-4-hydroxyphenyl) phosphothionatetris (3-phenyl-5-tert-butyl-4-hydroxyphenyl) phosphothionate In apreferred embodiment of this invention both R and R are alpha-branchedhydrocarbyl radicals. Some representative examples of these compoundsare:

tris 3,5 -diisopropyl-4-hydroxyphenyl phosphothionate tris 3,5-dicyclohexyl-4-hydroxyphenyl phosphothionate tris( 3 ,5-di-sec-butyl-4-hydroxyphenyl phosphothionate tris3-isopropyl-5-tert-butyl-4-hydroxyphenyl) phosphothionate tris3-tert-butyl-5- a-methylbenzyl -4-hydroxyphenyl) phosphothionate tris3-tert-butyl-S-cyclohexyl-4-hydroxyphenyl) phosphothionate tris 3-tert-dodecyl-S-sec-octadecyl-4-hydroxyphenyl) phosphothionate tris3-tert-nonyl-5-sec-octyl-4-hydroxyphenyl) phosphothionate In a morepreferred embodiment of this invention both R and R are tertiary alkylradicals These may be illustrated by the folowing compounds:

tris 3,5 -di-tert-amyl-4-hydroxyphenyl phosphothionate tris 3,5-di-tert-octyl-4-hydroxyphenyl phosphothionate tris 3,5-di-tert-dodecyl4-hydroxyphenyl phosphothionate tris 3,5-di-tert-octadecyl-4-hydroxyphenyl) phosphothionate tris 3 ,S-di-(0:,a-d11116ihY1b611ZYi -4-hydroxyphenyl phosphothionate tris3-tert-butyl-5-tert-octyl-4-hydroxyphenyl) phosphothionate tris3-tert-butyl-5- u,a-dimethylbenzyl -4-hydroxyphenyl -phosphothionatetris 3-tert-amyl-S-tert-octadecyl-4-hydroxyphenyl) phosphothionate In amost preferred embodiment of this invention thetris(3,5-dihydrocarbyl-4-hydroxyphenyl)phosphothionate istris(3,5-di-tert-butyl-4-hydroxyphenyl)phosphothionate.

In the foregoing description many of the preferred R and R radicals arereferred to as alpha-branched radicals. These are radicals wherein thecarbon atom through which the radical bonds to the benzene ring is alsobonded to at least two carbon atoms other than the carbon atom in thebenzene ring. In other words, alpha-branched radicals are those commonlyreferred to as secondary or tertiary radicals such as the isopropyl andtert-butyl radicals.

A preferred method of preparing the additive compounds is by the directreaction of elemental sulfur with the desired tris( 3,5 dihydrocarbyl 4hydroxyphenyl)- phosphite. This latter phosphite is readily prepared bythe reaction of phosphorous trichloride with 2,6-dihydrocarbyl-p-hydroquinones, as described in copending application Ser. No.505,990, filed Nov. 1, 1965 now abandoned. This preferred method can becarried out without a solvent, although the use of a solvent ispreferred. Suitable solvents are those in which the phosphite is solubleand which are inert to the reactants or products inder the reactionconditions. Some examples of these 11'6 ethers such as diethyl ether,ethylbutyl ether, di-npropyl ether, ethyleneglycoldiethyl ether,diethylenegly- :oldimethyl ether, and the like; esters such as ethylace- ;ate, amyl acetate, ethyl butyrate, and the like; and hydrocarbonssuch as hexane, heptane, isooctane, kerosene, petroleum ether, mineralspirits, and the like. The preferred solvents are hydrocarbons having aboiling point of from about 50 to about 200 C. Still more preferredhydrocarbon solvents are the aromatic hydrocarbons having a boilingpoint of from about 80 to about 200 C. Examples of highly preferredaromatic solvents are toluene and xylene.

The above sulfur reaction is carried out at temperature high enough thatthe reaction proceeds at a reasonable rate, but not so high as to causedegradation of the product. The preferred temperature range is fromabout 50 to 200 C., and a more preferred temperature range is from about75 to 175 C.

The reaction of the sulfur is usually complete in from 1 to 8 hours,depending upon the phosphite reactant and the temperature employed. Inthe more preferred temperature range the reaction is usually complete infrom about 2 to 6 hours.

The product is easily recovered by vaporizing off the solvents. If apurified form of the product is required, the product can berecrystallized from a suitable solvent, such as isopropyl alcohol.

Another method of preparing the additive compounds is by reacting a2,6-dihydrocarbyl-p-hydroquinone with a phosphorus thiohalide. Althoughany of the phosphorus thiohalides may be employed, the preferredreactants are phosphorus thiobromide and phosphorus thiochloride, andespecially phosphorus thiochloride because of its low cost, availabilityand excellent results obtained with its use.

The 2,6-dihydrocarbyl-p-hydroquinones can be prepared by any of themethods available in the art such as the oxidation of the corresponding2,6-dihydrocarbylp-aminophenol to the 2,6-dihydrocarbyl-benzoquinonefollowed by reduction to the 2,o-dihydrocarbyl-p-hydroquinone. Anespecially useful method for preparing the preferred hydroquinones isthrough the air oxidation of the proper 2,6 di tert alkyl 4 tertbutylphenol. The air oxidation of such compounds leads to2,6-ditert-alkyl-p-benzoquinones which are readily converted to thecorresponding hydroquinone by reduction. This method is described indetail in US. 3,213,114, issued Oct. 19, 1965.

The stoichiometry of the reaction requires three moles of the2,6-dihydrocarbyl-p-hyroquinone per mole of phosphorus thiohalide.Slightly more or slightly less of the hydroquinone can be employed. Apreferred range is from about 2.8 to 3.1 moles per mole or phosphorusthiohalide. A most preferred range is from about 2.9 to 3 moles of2,6-dihydrocarbyl-p-hydroquinone per mole of phosphorus thiohalide.

The reaction between the hydroquinone and the phosphorus thiochloridecan be conducted by adding the phosphorus thiochloride to thehydroquinone or by adding the hydroquinone to the phosphorusthiochloride. The preferred method is to add the phosphorus thiochlorideto the hydroquinone in a mole ratio of about one mole of phosphorusthiochloride to 3 moles of the hydroquinone, thus avoiding any excess ofphosphorus thiochloride which might undergo undesirable side reactionswith the tris- (3,5-dihydrocarbyl-4-hydroxyphenyl)phosphothionate.

The reaction may be conducted in the presence or absence of a solvent.Usually it is preferred to employ a solvent because this makes it easierto moderate the reaction and also to purify the product. Preferredsolvents are the same as those preferred in the sulfur process.

The reaction should be conducted at a temperature high enough so thatthe reaction proceeds at a reasonable rate, but not so high as to causedegradation of the 4 product. A preferred temperature range is fromabout zero degrees up to about 200 C. and a most preferred temperaturerange is from about 20 to 30 C.

The reaction involves the evolution of a hydrogen halide, for example,HCl, and thus can be conducted in the presence of a hydrogen halideacceptor. Especially suitable hydrogen halide acceptors are the tertiaryamines such as pyridine or triethylamine.

The reaction may be conducted in the presence of air, although it isusually preferred to carry the reaction out under a relatively inertatmosphere. An inert atmosphere removes the danger of explosions,minimizes the danger of solvent vapor explosions and lessens thelikelihood of contaminating the product through oxidation, Although theprocess can be conducted at temperatures both below and aboveatmospheric pressure, it is normally conducted at atmospheric pressure.

The addition of the phosphorus thiohalide to the 2,6-dihydrocarbyl-p-hydroquinone usually takes from about 15 minutes toseveral hours, depending upon the size of the reaction and theefficiency of heat removal. The addition time is not critical and can becarried out at as high a rate as permitted by the cooling meansavailable. Under normal conditions the addition is readily completed infrom about 30 minutes to an hour. Preferably, the reaction is stirred atthe reaction temperature for a short period following the completion ofthe addition of the reactants. Under most circumstances the reaction iscomplete in from about 0.5 to 8 hours following completion of addition.A preferred reaction time is from about one to 4 hours, and a mostpreferred reaction time is from about 2 to 3 hours.

The product may be recovered by any of the means known to those skilledin the art. One useful method employed when a tertiary amine hydrogenhalide acceptor is employed is to first filter off the tertiary aminehydrogen halide complex, following which all solvent is distilled fromthe filtrate, leaving a semiliquid residue. This residue is thendissolved in a hot aliphatic hydrocarbon such as hexane and, uponcooling, the tris(3,5-dihydrocarbyl-4- hydroxyphenyl)phosphothionatewill crystallize in high purity and good yield.

When the reaction is conducted without an amine hydrogen halideacceptor, the reaction mass can be merely washed with water at the endof the reaction period to remove any residual hydrogen halide. It isthen preferably washed with a slightly basic solution (e.g., dilute NaCO solution) to neutralize any remaining acid.

When a high purity product is not required the product can be recoveredby merely evaporating any solvent employed and using the residue as is.In still another embodiment the solution of the stabilizer may be useddirectly in blending with the organic materials requiring stabilization.Thus, when the reaction is conducted in a toluene solvent, the toluenesolution of the stabilizer may be washed and neutralized to removeacidic material and then sprayed directly onto, for example, bulkpolypropylene. The solvent is then evaporated off and the bulkpolypropylene. The solvent is then evaporated ofif and the bulkpolypropylene is ready for processing (e.g., molding, extrusion, and thelike).

The following examples will serve to illustrate the preparation of theadditive compounds of the present invention. All parts are parts byweight unless otherwise specified.

Example 1 To a reaction vessel fitted with stirrer, thermometer, refluxcondenser and heating means was added parts of xylene, 10 parts oftris(3,5-di-tert-butyl-4-hydroxyphenol)phosphite and 0.5 part ofelemental sulfur powder. While stirring, the reaction mass was heated to132 C. and maintained at that temperature for 4 hours and 20 minutes. Itwas then cooled and the solvent distilled off under vacuum. The residuewas recrystallized from isopropyl alcohol, yielding a crystallineproduct melting at 1947 C. Elemental analysis showed it to contain 69.1percent carbon, 8.8 percent hydrogen, 4.33 percent phosphorus and 4.52percent sulfur, which confirmed its identity as tris(3,5-di-tert-butyl-4-hydroxyphenyl)phosphothionate.

Other additive compounds of this invention can be prepared following theabove example, but using equal mole amounts of different phosphites. Forexample, tris(3,5- diisopropyl-4-hydroxyphenyl)phosphothionate can beprepared from tris(3,5-di isopropyl-4-hydroxyphenyl)phosphite. Likewise,tris(3,5-di-cyclohexyl-4-hydroxyphenyl) phosphothionate is obtained fromtris(3,5-di-cyclohexyl- 4-hydroxyphenyl)phosphite. The use oftris(3-tert-butyl- 5-cyclohexyl-4-hydroxyphenyl)phosphite yields tris(3-tert-butyl 5 -.cyclohexyl 4 hydroxyphenyl)phosphothionate.

Example 2 To a reaction vessel fitted with stirrer, thermometer, liquidaddition means and cooling means is added 8.6 parts of2,6-di-tert-butyl-p-hydroquinone, 3.9 parts of triethylamine and 70parts of diethyl ether. The vapor space above the liquid reactants isdisplaced with a nitrogen atmosphere which is maintained during theremainder of the reaction. A solution of 2.1 parts of phosphorusthiochloride in 18 parts of diethyl ether is added to the reactionvessel while stirring. The reaction temperature is maintained at about30 C. during this addition. The reaction is then stirred for about 12hours, during which period a triethylamine hydrochloride precipitateforms. This precipitate is filtered ofi and the ether solvent removedfrom the filtrate by evaporation under vacuum (about mm. Hg). Theresidue remaining is recrystallized from a methanol water mixture,yielding tris(3,5-ditert-bu tyl-4-hydroxyphenyl phosphothionate.

Example 3 To a reaction vessel equipped as in Example 2 is added 667parts of 2,6-di-tert-butyl-p hydroquinone and 1500 parts of toluene.Nitrogen is passed through the vessel until all air has been removed anda nitrogen atmosphere is maintained throughout the remainder of thereaction. Whie stirring, the vessel contents are heated to the refluxtemperature of the solvent. While maintaining the reaction at refluex,169.0 parts of phosphorus thiochloride are added over a one hour period.Cooling is effected by reflux of the solvent. Following the phosphorusthiochloride addition, the reaction is refluxed for two additionalhours. It is then allowed to cool and immediately upon dropping below 90C., 1000 parts of water are added to the reaction vessel and the mixturestirred for 15 minutes. The water is drained off and the reactants arethen washed with 1000 parts of a 5 percent sodium carbonate solution.This solution is drained off and the toluene solvent is then removed byreducing the pressure in the reaction vessel to 50 mm. and slowlydistilling out the toluene until the reaction vessel contents reach 150C. The remaining material is dissolved in a minimum amount of hot hexaneand the hexane solution is then cooled to 0 C., causing the product toprecipitate, forming a slurry. The reaction mass is then filtered andthe product, tris(3,5-di-tert-butyl- 4-hydroxyphenyl)phosphothionate, isobtained.

Example 4 To a reaction vessel equipped as in Example 1 is added 954parts of 2,6-di(a-methylbenzyl)-p-hydroquinone and 3000 parts of xylene.While stirring, 164 parts of phosphorus thiochloride are added over a.period of 4 hours, while maintaining the reaction temperature at C.Following the phosphorus thiochoride addition, the reaction contents arestirred for 7 additional hours at 30 C. and then the temperature isslowly raised to 100 C. during an additional one hour period. Thereaction mass is then cooled and washed twice with 1000 parts of watereach. The reaction mass is then treated with 1000 parts of a 5 percentsodium carbonate solution. Following this, the xylene solvent is removedby distilling out the solvent at 30 mm. of pressure until the reactionvessel attains a temperature of C. The residue is recrystallized from aminimum quantity of petroleum ether (B.P. 6070 C.), yieldingtris(3,5-di(a-methylbenzyl) 4 hydroxyphenyl) phosphothionate.

In the above example equal mole quantities of other 2,6-dihydrocarbyl-p-hydroquinones can be employed to give the correspondingtris(3,S-dihydrocarbyl-4-hydroxyphenyl)phosphothionate. For example, theuse of 2,6-diisopropyl-p-hydroquinone yieldstris(3,5-diisopropyl-4-hydroxyphenyl)phosphothionate. The use of2,6-di-sec-butylp hydroquinone yields tris(3,5-di-sec-butyl 4hydroxyphenyl)phosphothionate. The use of2,6-di-tert-octy1-phydroquinone yieldstris(3,S-di-tert-octyl-4-hydroxyphenyl)phosphothionate. The use of2,6-dicyclohexyl-p-hydroquinone yields tris(3,5-dicyclohexyl 4hydroxyphenyl) phosphothionate. The use of2,6-di-tert-octadecyl-p-hydroquinone yieldstris(3,5-di-tert-octadecyl-4-hydroxyphenyl) phosphothionate. The use of2-methyl-6-(a,a-dimethylbenzyl)-p-hydroquinone yields tris[3methyl-5-(a,u dimethylbenzyl) 4 hydroxyphenyl]phosphothionate. The useof 2-(2,4-di-tert-butylphenyl)-6-tert-dodecyl-p-hydroquinone yieldstris[3 (2,4-di-tert-butylphenyl) 5tertdodecyl-4-hydroxyphenyl]phosphothionate.

In like manner, equal mole quantities of other phosphorus thiohalidescan be used, such as phosphorus thiobromide, with good results.

The compounds of this invention are extremely useful as antioxidants ina wide variety of organic material normally susceptible to deteriorationin the resence of oxygen. Thus, liquid hydrocarbon fuels such asgasoline, kerosene and fuel oil are found to possess increased storagestability when blended with a stabilizing quantity of an additive ofthis invention. Likewise, hydrocarbon fuels containing organometallicadditives such as tetraethyllead, tetramethyllead, methylcyclopentadienyl manganese tricarbonyl, cyclopentadienyl nickelnitrosyl, ferrocene and iron carbonyl have appreciably increasedstability when treated with the additives of this invention.Furthermore, lubricating oils and functional fluids, both those derivedfrom naturally occurring hydrocarbons and those synthetically prepared,have greatly enhanced stability by the practice of this invention. Theadditives of this invention are extremely useful in stabilizingantiknock fluids against oxidative degradation. For example, thestabilizing additives of this invention find utility in stabilizing atetraethyllead antiknock fluid which contains ethylenedichloride andethylenedibromide.

The additives of this invention are eflective in stabilizing rubberagainst degradation caused by oxygen or ozone. As used in thedescription and claims, the term rubber is employed in a generic senseto define a high molecular weight plastic material which possesses highextensibility under load coupled with the property of forciblyretracting to approximately its original size and shape after the loadis removed. Some examples are acrylic rubber, butadiene-styrene rubber(SBR), chloroprene, chlorosulfonated polyethylene, fluorocarbon rubbers,isobutylene-isoprene (IIR), isoprene, butadiene, nitrile-butadienerubber, polyisobutylene rubber, polysulfide rubbers, silicone rubbers,urethanes, India rubber, reclaimed rubber, balata rubber, gutta percharubber, and the like. Both natural rubber and synthetic rubbers such asneoprene, SBR rubber, EPT rubber, GR-N rubber, chloropene rubber,polyisoprene rubber, EPR rubber, and the like, are greatly stabilizedthrough the practice of this invention.

The compounds of this invention are also useful in protecting petroleumwax against degradation. The additives also find use in thestabilization of fats and oils of animal and vegetable origin which tendto become rancid during long periods of storage because of oxidativedeterioration.

Typical representatives of these edible fats and oils/ are linseed oil,cod liver oil, castor oil, soy bean oil, rapeseed oil, coconut oil,olive oil, palm oil, corn oil, sesame oil, peanut oil, babassu oil,butter, lard, beef tallow, and the like.

The compounds of this invention are superior antioxidants for highmolecular Weight polyolefins such as polyethylene (both high pressureand so-called Ziegler type polyethylene), polybutene, polybutadiene(both cis and trans), and the like.

One of the features of the present stabilizers is that they do not causediscoloration when used in transparent, White,

or light-colored organic materials such as white rubber.

or plastics such as polyethylene, polypropylene, and the like.

The amount of stabilizer used in the organic compositions of thisinvention is not critical, as long as a stabilizing quantity is present,and can vary from as little as 0.001 Weight percent to about weightpercent. Generally, excellent results are obtained when from 0.1 toabout 3 weight percent of the stabilizer is included in the organiccompositions.

The following examples serve to illustrate the use of the stabilizers ofthe present invention in stabilizing some representative organicmaterials normally subject to deterioration in the presence of oxygen orozone.

Example 5 A rubber stock is prepared containing the following To theabove base formula is added one part by weight of tris(3,5di-tert-butyl-4-hydroxyphenyl)phosphothionate and, following this,individual samples are cured for 20, 30, 45 and 60 minutes, respectivelyat 274 C. After cure, all of these samples remain white in color andpossess excellent tensile strength. Furthermore, they are resistant todegradation caused by either oxygen or ozone on aging.

Example 6 A synthetic rubber master batch (comprising 100 parts of GR-Srubber having an average molecular Weight of 60,000, 50 parts of mixedzinc propionate-stearate, 50 parts of carbon black, 5 parts of road tar,2 parts of sulfur and 1.5 parts of mercaptobenzothiazole is prepared. Tothis is added 1.5 parts of tri(3,5-(a-methylbenzyD-4-hydroxyphenyl)phosphothionate. This composition is then cured for 60minutes employing 45 p.s.i.g. of steam pressure. The resulting syntheticrubber possesses resistance to oxygen and ozone induced degradation.

Example 7 A *butadiene acrylonitrile copolymer is prepared from 68percent 1,3-butadiene and 32 percent acrylonitrile. Two percent, basedon the weight of the copolymer, of tris(3,5-diisopropyl4-hydroxyphenyl)phosphothionate is added as an aqueous emulsion to thelatex obtained from emulsion copolymerization of the butadiene andacrylonitrile monomers. The latex is coagulated with aluminum sulfateand the coagulum, after washing, is dried for hours at 70 C. Thesynthetic copolymer so obtained is resistant to oxidative degradation.

Example 8 Three percent of tris(3,5-di-tert-octyl-4-hydroxyphenyl)phosphotionate as an emulsion in sodium oleate is added to a rubber-likecopolymer of 1,3-butadiene and styrene containing percent styrene. Theresulting synthetic elastomer possesses enhanced stability.

Example 9 To a master batch of GR-N synthetic rubber containing parts ofG'R-N rubber, 5 parts of zinc stearate, 50 parts of carbon black, 5parts of road tar, 2 parts of sulfur and 2 parts ofmercaptobenzothiazole is added 5 percent, based on weight, oftris(3,5-di-sec-butyl-4-hydroxyphenyl)phosphothionate. After curing, asynthetic rubber is obtained of improved oxidative stability.

Example 10 To a master batch of polyethylene having an average molecularweight of 1,000,000, a tensile strength of 6,700 p.s.i., a Shore Dhardness of 74 and a softening temperature under low load of C., isadded 5 percent of tris(3,5-di-tert-butyl 4hydroxyphenyl)phosphothiomate. The resulting polyethylene possessesstability against oxidative degradation and shows no tendency to yellowafter extensive aging.

Example 11 A linear polyethylene having a high degree of crystallinity(93 percent), and less than one branched chain per 100 carbon atoms, adensity of about 0.96 gram per ml. and which has about 1.5 double bondsper 100 carbon atoms, is mixed with 0.005 weight percent oftris(3,5-dicyclohexyl-4-hydroxyphenyl)phosphothionate. The resultingpolyethylene is found to possess stability against oxidativedegradation.

Example 12 To 100 parts of an ethylenepropylene terpolymer is added 3parts of tris(3-tert-amyl-5-tert-octyl-4-hydroxyphenyl)phosphothionate,resulting in an ethylenepropylene terpolymer of enhanced stability.

Example 13 To 100 parts of an ethylenepropylene rubber is added 2 partsof tris(3-tert-nonyl-5-sec-octyl-4-hydroxyphenyl) phosphothionate,resulting in an EPR rubber stock of improved stability.

Example 14 After the polymerization of polypropylene in a hexane solventemploying a Ziegler catalyst, the catalyst is neutralized with water andtris(3,5-di-tert-butyl-4-hydroxyphenyl)phosphothionate is added to themixture in quantities such that, after evaporation of the solvent, aZiegler polypropylene is obtained containing 2 percent oftris(3,5-di-tert-butyl 4-hpdroxyphenyl)phosphothionate. Thispolypropylene possesses excellent stability against degradation causedby oxygen or ozone. Furthermore, this polypropylene is found to resistdegradation at elevated temperatures, even in the presence of oxygen.During this high temperature aging the highly crystalline Zieglerpolypropylene shows no tendency to discolor.

Example 15 To 1,000 parts of a gasoline containing 26.6 percentaromatics, 20.8 percent olefins, 52.6 percent saturates and having anAPI gravity of 62.1 is added 10 parts of tris(3-tert-butyl-5-cyclohexyl4 hydroxyphenyl)phosphothionate. The resulting gasoline is stable.

Example 16 To 10,000 parts of gasoline containing 8.6 percent aromatics,7.9 percent olefins, 83.5 percent saturates and having an API gravity of68.5 is added 200 parts of tris(3-methyl-5-cyclohexy1 4hydroxyphenyl)phosphothionate. The resulting gasoline is stable againstoxidative degradation.

Example 17 To 10,000 parts of a gasoline containing 20.0 percentaromatics, 41.2 percent olefins, 38.8 percent saturates and containingadditionally 1.5 grams of manganese per gallon as methylcyclopentadienyl manganese tricarbonyl is added 300 parts oftris(3-phenyl-5-tert-butyl-4-hydroxyphenyl)phosphothionate. Theresulting gasoline containing a manganese antiknock was resistant tooxidative degradation.

Example 18 To 10,000 parts of a gasoline containing 20.5 percentaromatics, 32.9 percent olefins and 46.6 percent saturates andcontaining 2.39 grams per gallon of tetraethyllead and one theory ofchlorine as ethylenedichloride and 0.5 theory of bromine asethylenedibromide is added 500 parts of tris(3,5-di-tert-butyl 4hydroxyphenyl)phosphothionate. The resulting gasoline containing a leadantiknock and halogen scavenger is resistant to oxidative degradation.Not only this, but it is also found when used to give prolonged sparkplug life due to the presence of the phosphorus containing antioxidant.

Example 19 To 10,000 parts of gasoline containing 38.1 percentaromatics, 7.3 percent olefins and 54.6 percent saturates and whichcontains 3.17 grams per gallon of lead as tetramethyllead, one theory ofchlorine as ethylenedichloride, 0.5 theory of bromine asethylenedibromide and 0.2 theory of phosphorus astris(,9-chloroisopropyl)thiono phosphate is added 50 parts oftris[3-tert-butyl-5-(a,udimethylbenzyl)-4 hydroxyphenyl]phosphothionate. The resulting gasoline is resistant to degradation andgives prolonged spark plug life on use.

Example 20 An antiknock fluid composition is prepared by mixing together61.5 parts of tetraethyllead, 17.9 parts of ethylenedibromide, 188 partsof ethylenedichloride and 1.3 parts of tris(3,5-di-tert-butyl-4hydroxyphenyl)phosphothionate, resulting in a stable antiknock fluidcomposition.

Example 21 To 1,000 parts of a commercial diesel fuel having a cetanenumber of 42, is added parts of amyl nitrate and 4 parts oftris[3-n-propyl-5-(u-methylbenzyl)-4-hydroxyphenyl]phosphothionate,resulting in a diesel fuel of high resistance to oxidative deteriorationwhich does not form gum or sludge on storage.

Example 22 To 1,000 parts of a solvent refined neutral oil (95 viscosityindex and 200 SUS at 100 F.) containing 6 percent of a commercialmethacrylate type B 1 improver is added 5 percent oftris[3,5-di(a-methylbenzyl)-4-hydroxyphenyl]phosphothionate, resultingin a stable lubricating oil.

Example 23 To a solvent refined crankcase lubricating oil having aviscosity index of 95 and a SAE viscosity of is added 0.1 percent oftris(3,5-di-tert-dodecyl-4-hydroxyphenyl) phosphothionate. The resultingoil was stable against oxidative degradation.

Example 24 To 100,000 parts of a petroleum hydrocarbon oil having agravity of 303 API at 60 F., viscosity of 178.8 SUS at 100 F., aviscosity index of 154.2, and containing 1,000 parts of the reactionproduct of an alkenyl succinic anhydride where the alkenyl group has amolecular weight of 2,000, with a polyethylene amine, is added 200 partsof tris(3 tert amyl-5-tert-octadecyl-4-hydroxyphenyl) phosphothionate.The resulting lubricating oil possesses excellent dispersancy and isresistant to oxidative degradation.

Example 25 To 100,000 parts of a commercially available pentaerythritolester having a viscosity at F. of 22.4 centi stokes and known under thetradename of Hercoflex 600 is added 400 parts oftris(3,5-di-cyclohexyl-4-hydroxyphenyl)phosphothionate. The resultingsynthetic lubricating oil possesses improved resistance againstoxidative deterioration.

Example 26 To 100,000 parts of dioctyl sebacate having a viscosity at210 F. of 36.7 SUS, a viscosity index of 159, and a molecular weight of427, is added 250 parts of tris(3- phenyl 5tert-butyl-4-hydroxyphenyl)phosphothionate, resulting in a syntheticdiester lubricating oil having improved resistance to oxidativedegradation.

Example 27 To 1,000 parts of a commercial coconut oil is added 5 partsof tris[3-tert-butyl-5-(a-methylbenzyl)-4-hydroxyphenylJphosphothionate,resulting in a vegetable oil with good aging characteristics.

Example 28 To 100,000 parts of lard is added 100 parts of tris(3- tertbutyl 5-cyclohexyl-4-hydroxyphenyl)phosphothionate, resulting in a lardhaving resistance to rancidity.

The stabilizing additives of this invention are eminently useful asstabilizers in polyolefins such as polyethylene, polypropylene, and thelike. In this use they function as antioxidants, antiozonants and alsoas thermal stabilizers. They are extremely long lasting and highlyresistant to the formation of color.

In order to demonstrate their vastly superior stabilization effect,tests were conducted using a commercial polypropylene. These tests areknown as Oven Aging Tests and are recognized in the plastic industry asan accurate guide to oxidative stability. In these tests small specimensof polypropylene are prepared containing the test stabilizer. These testspecimens are placed in an air circulating oven maintained at C. Fivereplicates are made of each polypropylene-stabilizer composition and thetest criteria is the time and hours until three of the five replicatesshow signs of deterioration. Deterioration is evidenced by cracking,discoloration or any visual appearance of change in the specimen.

Test specimens are prepared by mixing the test stabilizers withpolypropylene powder for 3 minutes in a Waring Blendor. The mixture isthen molded into a 6" x 6" sheet with thickness of 5, 25 and 62 mils.This is accomplished in a molding press at 400 F. under 5,000 psi.pressure. Each sheet is then cut into /2" x 1 test specimens in order toobtain the five replicate samples. These samples are then subjected tothe Oven Aging Tests.

In order to compare the stabilizing additives of this invention testswere carried out employing several commercially accepted stabilizersalong with the preferred stabilizer of the present invention. Theresults obtained are shown in the following table.

that have been used commercially. The present comwherein n is an integerfrom 1 to 5, and R is selected from the group consisting of alkylradicals containing from 1 'to 20 carbon atoms, aryl radicals containingfrom 6 to 20 carbon atoms, aralkyl radicals containing from 7 to 20carbon atoms and cycloalkyl radicals containing from 6 to 20 carbonatoms. In the preferred synergist n is an integer from 1 to 3 and R isselected from the group consisting of alkyl radicals containing from 10to 18 carbon atoms. The most preferred synergists aredilaurylthiodipropionate and distearylthiodipropionate.

The ratio of synergist to stabilizing compound should be adjusted togive the desired protection at the least cost. Mixtures containing from1 percent synergist and 99 percent stabilizer to those containing 99percent synergist and 1 percent stabilizer can be employed. Best resultsare usually obtained with stabilizing mixtures containing from 50 to 66percent synergist and from 34 to 50 percent stabilizing compound.

The synergists can be employed to obtain increased stability using thesame concentration of stabilizer or they can be employed to obtain thesame stability with less of the stabilizer. Synergists are especiallyuseful in this latter application. Thus, althoughdilaurylthiodipropionate (DLTDP) is only moderately effective -by itselfin stabilizing polypropylene, when used with a compound of the presentinvention a synergist interaction occurs, resulting in a degree ofstability totally unexpected from the amount of stabilizers employed.

Following are some examples of the synergistic stabilizing compositionsof the present invention.

Percent Tris(3,5 di tert-butyl 4 hydroxypheny1)phosphothionate 33Dilaurylthiodipropionate 67 Tris(3 methyl 5tert-butyl-4-hydroxyphenyl)phosphothionate t 50 Dihexylthiodiacetate 50Tris(3 ethyl S-isopropyl-4-hydroxyphenyl)phosphothionate 1Diheptylthiodivalerate 99 Tris(3 methyl 5cyclohexyl-4-hydroxyphenyl)phosphothionate 99Di-n-octyl-thiodipropionate 1 Tris 3 methyl-S- ot-methylbenzyl)-4-hydroxyphenyl) phosphothionate 75 Didecylthiodiacetate 25 Tris(3methyl 5 (a,u-dimethylbenzyl)-4-hydroxyphenyl)phosphothionate 25Diundecylthiodibutyrate 75 Tris(3,5 dicyclohexyl4-hydroxyphenyl)phosphothionate 25 Dioctadecylthiodipropionate 7S Tris(3tert butyl 5 (u-methylbenzyl)-4-hydroxyphenyl) phosphothionate 80Dinonadecylthiodibutyrate 20 Tris(3 tert dodecyl 5 sec-octadecyl 4hydroxyphenyl)phosphothionate 60 Dieicosylthiodipropionate 40 Tris(3,5di tert butyl 4-hydroxyphenyl)phosphothionate l0Dilaurylthiodipropionate Tris(3,5 di tert butyl 4hydroxyphenyl)phosphothionate 90 Dilaurylthiodipropionate 10 Tris(3,5 ditert butyl 4 hydroxyphenyl) phosphothionate 30 Distearylthiodipropionate70 The above synergistic stabilizer compositions are beneficiallyemployed in any of the previously described organic materials normallysusceptible to deterioration due to the effect of oxygen or ozone. InExamples 5 through 28, each of the above synergistic compositions can besubstituted for the stabilizing compound of the present invention nowshown, resulting in an organic composition of increased resistance todegradation from the effects of oxygen or ozone.

Having fully described new compositions of matter eminently useful instabilizing organic materials and having further described synergisticcombinations of these stabilizers with sulfur compounds and furthershown use of these combinations in stabilizing organic material, it isintended that this invention should be limited only within the spiritand scope of the following claims.

I claim:

1. Organic material normally susceptible to deterioration due to theeffects of oxygen, containing a stabilizing quantity of an antioxidantcompound, said compound having the formula:

wherein R is selected from the group consisting of alphabranched alkylradicals containing from 3 to 18 carbon atoms, alpha-branched aralkylradicals containing from 8 to 18 carbon atoms and cycle-alkyl radicalscontaining from 6 to 18 car-bon atoms; and R is selected from the groupconsisting of alkyl radicals containing from 1 to 18 carbon atoms,aralkyl radicals containing from 7 to 18 carbon atoms, aryl radicalscontaining from 6 to 18 carbon atoms and cycloalkyl radicals containingfrom 6 to 18 carbon atoms.

2. The composition of claim material is rubber.

3. The composition of claim material is gasoline.

4. The composition of claim material is a lubricating oil.

5. The composition of claim material is an antiknock fluid.

6. The composition of claim material is a polyolefin.

7. The composition of claim 6 wherein said polyolefin is polyethylene.

8. The composition of claim 6 wherein said polyolefin is polypropylene.

9. The composition of claim 8 wherein said stabilizing quantity is fromabout 0.001 to about 5 weight percent and wherein said compound istris(3,5-di-tert-butyl-4-hydroxyphenyl)phosphothionate.

10. A stabilizing composition comprising from 1 to 99 weight percent ofa compound of claim 1 and from 1 to 99 weight percent of a compoundhaving the formula:

wherein n is an integer from 1 to 5, and R is selected from the groupconsisting of alkyl radicals containing from 1 to 20 carbon atoms, arylradicals containing from 1 wherein said organic 1 wherein said organic 1wherein said organic 1 wherein said organic 1 wherein said organic 6 to20' carbon atoms, aralkyl radicals containing from 7 to 20 carbon atomsand cycloalkyl radicals containing from 6 to 20 carbon atoms.

11. The stabilizing composition of claim 10 wherein R and R aretert-butyl groups, n is 2 and R is the lauryl group.

12. Organic material normally susceptible to deterioration due to theeffects of oxygen, containing a stabilizing quantity of the stabilizingcomposition of claim 10.

13. The composition of claim 12 wherein R and R are tert-butyl groups, nis 2 and R is the lauryl group.

14. The composition of claim 13 wherein said organic material is apolyolefin.

15. The composition of claim 14 wherein said polyolefin ispolypropylene.

References Cited UNITED STATES PATENTS 5/1939 Humphreys 252--46.6 1/1962 Thompson 26045.995 X 8/1964 Knapp et a1 252-386 X 1/ 1968 Gleim etal 26045.95 X 8/1968 Hecker et a1. 26045.95 X

DANIEL E. WYMAN, Primary Examiner. 10 W. CANNON, Assislant Examiner.

US. Cl. X.R.

